1. Field of the Invention
The present invention relates to an apparatus and a method for recording data onto an optical disc.
2. Description of Related Art
Known optical disc standards for optically recording and reproducing data using an optical head include the CD (Compact Disc) and DVD (Digital Versatile Disc) standards. DVDs have the same disc diameter as CDs to secure mechanical compatibility therebetween and also provide a higher recording density than CDs to satisfy a need for higher capacity.
DVD drives for reproducing such DVDs maintain capability with CDs and are therefore capable of reproducing CDs as well.
Recordable optical discs can be realized in both CDs and DVDs. While there are presently only two common standards for recordable CD discs, the CD-R (Recordable) or CD-RW (Rewritable) standards, various recordable disc systems now coexist such that a de facto DVD standard has not been established.
Further, despite the disadvantage that the recording method of the CD standard allows only a much smaller of data to be stored on a disc than the DVD standard recording method, the existence of the recordable CD standards described above has led to the mass marketing of inexpensive LSIs for CD-R and CD-RW recording signal processors. In addition, CD-R discs and CD-RW discs are also much less expensive than recordable DVD discs.
On the other hand, because the standard storage capacities of CD-R and CD-RW are 650 MB or 700 MB, there is a demand for a higher storage capacity so as to meet the current situation in which a file data amount processed by a personal computer is being increased.
Therefore, there has been proposed a method in which the length of recording marks composed of pits and lands to be recorded on a disc is reduced while the CD data format, namely a modulation code and an error correction code (ECC) for CDs are used, thereby increasing the data recording density compared to the line density specified by the CD standard and increasing storage capacity of the disc. (See Japanese Patent Laid-Open Publication No. 2002-25064)
According to the method disclosed in Japanese Patent Laid-Open Publication No. 2002-25064, there are advantages that an inexpensive mass-marketed recording signal processor LSI can be used, the system design can be simplified, and existing discs can be used.
According to this method, however, because the format efficiency is fixed according to a data format, it is not possible to perform high density disc recording by increasing the format efficiency. Consequently, when a laser beam (beam of focused laser light) having a wavelength which conforms to the CD standard is used for disc recording and reproduction, the length of recording marks cannot be reduced significantly due to the laser spot diameter, which in turn impairs attempts to increase the recording density.